Initial import

2026-02-14 15:59:31 +01:00
parent 05dcea3c2b
commit f1ecbfaf8d
19 changed files with 2675 additions and 0 deletions
--- a/protocol/aprs/packet.go
+++ b/protocol/aprs/packet.go
@@ -0,0 +1,481 @@
+package aprs
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var (
+	// ErrInvalidPacket signals a corrupted/unknown APRS packet.
+	ErrInvalidPacket = errors.New("aprs: invalid packet")
+
+	// ErrInvalidPosition signals a corrupted APRS position report.
+	ErrInvalidPosition = errors.New("aprs: invalid position")
+)
+
+// Payload is the raw payload contained within an APRS packet.
+type Payload string
+
+// Type of payload.
+func (p Payload) Type() DataType {
+	var t DataType
+
+	if len(p) > 0 {
+		t = DataType(p[0])
+	}
+
+	return t
+}
+
+func isDigit(b byte) bool {
+	return b >= '0' && b <= '9'
+}
+
+func (p Payload) Len() int { return len(p) }
+
+// Velocity details.
+type Velocity struct {
+	Course float64 // Degrees
+	Speed  float64 // Knots
+}
+
+// Wind details.
+type Wind struct {
+	Direction float64 // Degrees
+	Speed     float64 // Knots
+}
+
+// PowerHeightGain details.
+type PowerHeightGain struct {
+	PowerCode       byte
+	HeightCode      byte
+	GainCode        byte
+	DirectivityCode byte
+}
+
+// Power level (in Watts).
+func (p PowerHeightGain) Power() int {
+	w := int(p.PowerCode - '0')
+	if w <= 0 {
+		return 0
+	}
+	return w * w
+}
+
+// Height above ground (in meters).
+func (p PowerHeightGain) Height() float64 {
+	h := float64(p.HeightCode - '0')
+	if h <= 0 {
+		return 10
+	}
+	return math.Pow(2, h) * 10
+}
+
+// Gain level (in dBs).
+func (p PowerHeightGain) Gain() int {
+	d := int(p.GainCode - '0')
+	if d <= 0 {
+		return 0
+	}
+	return d
+}
+
+// Directivity angle.
+func (p PowerHeightGain) Directivity() float64 {
+	d := int(p.DirectivityCode - '0')
+	if d <= 0 {
+		return 0
+	}
+	return float64(d%8) * 45.0
+}
+
+// OmniDFStrength contains the omni-directional direction finding signal strength (for fox hunting).
+type OmniDFStrength struct {
+	StrengthCode    byte
+	HeightCode      byte
+	GainCode        byte
+	DirectivityCode byte
+}
+
+// Strength of the signal.
+func (o OmniDFStrength) Strength() int {
+	w := int(o.StrengthCode - '0')
+	if w <= 0 {
+		return 0
+	}
+	return w * w
+}
+
+// Height above ground (in meters).
+func (o OmniDFStrength) Height() float64 {
+	h := float64(o.HeightCode - '0')
+	if h <= 0 {
+		return 10
+	}
+	return math.Pow(2, h) * 10
+}
+
+// Gain level (in dBs).
+func (o OmniDFStrength) Gain() int {
+	d := int(o.GainCode - '0')
+	if d <= 0 {
+		return 0
+	}
+	return d
+}
+
+// Directivity angle.
+func (o OmniDFStrength) Directivity() float64 {
+	d := int(o.DirectivityCode - '0')
+	if d <= 0 {
+		return 0
+	}
+	return float64(d%8) * 45.0
+}
+
+// Packet contains an APRS packet.
+type Packet struct {
+	// Raw packet (as captured from the air or APRS-IS).
+	Raw string `json:"raw"`
+
+	// Src is the source address.
+	Src Address `json:"src"`
+
+	// Dst is the destination address.
+	Dst Address `json:"dst"`
+
+	// Path contains the digipeater path.
+	Path Path `json:"path,omitempty"`
+
+	// Payload is the raw payload.
+	Payload Payload `json:"payload"`
+
+	// Position encoded in the payload.
+	Position *Position `json:"position,omitempty"`
+
+	// Time encoded in the payload.
+	Time *time.Time `json:"time,omitempty"`
+
+	// Altitude encoded in the payload (in feet).
+	Altitude float64 `json:"altitude,omitempty"`
+
+	// Velocity encoded in the payload.
+	Velocity *Velocity `json:"velocity,omitempty"`
+
+	// Wind details encoded in the payload.
+	Wind *Wind `json:"wind,omitempty"`
+
+	// PHG are the power, height and gain details encoded in the payload.
+	PHG *PowerHeightGain `json:"phg,omitempty"`
+
+	// DFS are the direction finder strength details encoded in the payload.
+	DFS *OmniDFStrength `json:"dfs,omitempty"`
+
+	// Range encoded in the payload (in miles).
+	Range float64 `json:"range,omitempty"`
+
+	// Symbol encoded in the payload.
+	Symbol Symbol `json:"symbol"`
+
+	// Comment encoded in the payload.
+	Comment string `json:"comment,omitempty"`
+
+	// Unparsed data.
+	data string
+}
+
+// ParsePacket parses an APRS packet as captured from AX.25 or APRS-IS.
+func ParsePacket(raw string) (Packet, error) {
+	p := Packet{Raw: raw}
+
+	var i int
+	if i = strings.Index(raw, ":"); i < 0 {
+		return p, ErrInvalidPacket
+	}
+	p.Payload = Payload(raw[i+1:])
+
+	// Parse src, dst and path
+	var err error
+	var a = raw[:i]
+	if i = strings.Index(a, ">"); i < 0 {
+		return p, ErrInvalidPacket
+	}
+	if p.Src, err = ParseAddress(a[:i]); err != nil {
+		return p, err
+	}
+	var r = strings.Split(a[i+1:], ",")
+	if p.Dst, err = ParseAddress(r[0]); err != nil {
+		return p, err
+	}
+	if p.Path, err = ParsePath(strings.Join(r[1:], ",")); err != nil {
+		return p, err
+	}
+
+	// Post processing of payload
+	err = p.parse()
+	return p, err
+}
+
+func (p *Packet) parse() error {
+	s := string(p.Payload)
+	//log.Printf("parse %q [%c]\n", s, p.Payload.Type())
+
+	switch p.Payload.Type() {
+	case '!': // Lat/Long Position Report Format — without Timestamp
+		var o = strings.IndexByte(s, '!')
+		pos, txt, err := ParsePosition(s[o+1:], !isDigit(s[o+1]))
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.data = txt
+		if len(s) >= 20 {
+			p.Symbol[0] = s[9]
+			p.Symbol[1] = s[19]
+		}
+	case '=':
+		compressed := IsValidCompressedSymTable(s[1])
+		pos, txt, err := ParsePosition(s[1:], compressed)
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.data = txt
+		if compressed {
+			p.Symbol[0] = s[1]
+			p.Symbol[1] = s[10]
+		} else {
+			p.Symbol[0] = s[9]
+			p.Symbol[1] = s[19]
+		}
+	case '/', '@': // Lat/Long Position Report Format — with Timestamp
+		if len(s) < 8 {
+			return ErrInvalidPosition
+		}
+
+		var compressed bool
+		if s[7] == 'h' || s[7] == 'z' || s[7] == '/' {
+			if ts, err := ParseTime(s[1:]); err == nil {
+				p.Time = &ts
+			}
+			compressed = IsValidCompressedSymTable(s[8])
+			pos, txt, err := ParsePosition(s[8:], compressed)
+			if err != nil {
+				return err
+			}
+			p.Position = &pos
+			p.data = txt
+		} else if s[7] >= '0' && s[7] <= '9' {
+			ts, err := ParseTime(s[1:])
+			if err != nil {
+				return err
+			}
+			p.Time = &ts
+			compressed = IsValidCompressedSymTable(s[10])
+			pos, txt, err := ParsePosition(s[10:], compressed)
+			if err != nil {
+				return err
+			}
+			p.Position = &pos
+			p.data = txt
+		}
+		if compressed {
+			p.Symbol[0] = s[8]
+			p.Symbol[1] = s[17]
+		} else {
+			p.Symbol[0] = s[16]
+			p.Symbol[1] = s[26]
+		}
+	case ';':
+		pos, txt, err := ParsePosition(s[18:], !isDigit(s[18]))
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.data = txt
+	case '[':
+		pos, txt, err := ParsePositionGrid(s[1:])
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.data = txt
+	case '`', '\'':
+		pos, err := ParseMicE(s, p.Dst.Call)
+		if err != nil {
+			return err
+		}
+		p.Position = &pos
+		p.parseMicEData()
+
+		return nil // there is no additional data to parse
+	default:
+		pos, txt, err := ParsePositionBoth(s)
+		if err != nil {
+			if err != ErrInvalidPosition {
+				return err
+			}
+			p.Comment = s[1:]
+		} else {
+			p.Position = &pos
+			p.Comment = txt
+		}
+	}
+
+	if p.Position != nil {
+		if p.Position.Compressed {
+			return p.parseCompressedData()
+		}
+		return p.parseData()
+	}
+
+	return nil
+}
+
+func (p *Packet) parseMicEData() error {
+	// APRS PROTOCOL REFERENCE 1.0.1 Chapter 10, page 42 in PDF
+
+	s := string(p.Payload)
+
+	// Mic-E Message Type
+	var mt []string
+	var t string
+	for i := 0; i < 3; i++ {
+		mc := miceCodes[rune(p.Dst.Call[i])][1]
+		if strings.HasSuffix(mc, "(Custom)") {
+			t = messageTypeCustom
+		} else if strings.HasSuffix(mc, "(Std)") {
+			t = messageTypeStd
+		}
+		mt = append(mt, string(mc[0]))
+	}
+	switch t {
+	case messageTypeStd:
+		mt = append(mt, " (Std)")
+	case messageTypeCustom:
+		mt = append(mt, " (Custom)")
+	}
+	p.Comment = miceMsgTypes[strings.Join(mt, "")]
+
+	// Speed and Course.
+	speed := float64(int(s[4])-28) * 10
+	dc := float64(int(s[5])-28) / 10
+	unit := float64(int(dc))
+	speed += unit
+	course := dc - unit
+	course += float64(int(s[6]) - 28)
+	if speed >= 800 {
+		speed -= 800
+	}
+	speed = 1.852 * speed // convert speed from knots to km/h
+	if course >= 400 {
+		course -= 400
+	}
+
+	// Symbol
+	p.Symbol[0] = s[7]
+	p.Symbol[1] = s[8]
+
+	p.Comment += fmt.Sprintf(" (%.fkm/h, %.f°)", speed, course)
+
+	// Check whether there's additional Telemetry or Status Text data.
+	if len(s) == 9 {
+		return nil
+	}
+
+	if s[9] == ',' || s[9] == '\x1d' {
+		// TODO: Parse telemetry data.
+		return nil
+	}
+
+	// Parse MicE Status Text data.
+	// TODO: Parse additional data in the Status Text data:
+	// - Actual (custom) text message
+	// - Maidenhead locator
+	// - Altitude
+
+	return nil
+}
+
+func (p *Packet) parseCompressedData() error {
+	// Parse csT bytes
+	if len(p.data) >= 3 {
+		// Compression Type (T) Byte Format
+		// Bit: 7      | 6      | 5       | 4     3     | 2    1    0      |
+		//	-------+--------+---------+-------------+------------------+
+		//      Unused | Unused | GPS Fix | NMEA Source | Origin           |
+		//	-------+--------+---------+-------------+------------------+
+		// Val: 0      | 0      | 0 = old | 00 = other  | 000 = Compressed |
+		//	       |        | 1 = cur | 01 = GLL    | 001 = TNC BTex   |
+		//	       |        |         | 10 = CGA    | 010 = Software   |
+		//	       |        |         | 11 = RMC    | 011 = [tbd]      |
+		//	       |        |         |             | 100 = KPC3       |
+		//	       |        |         |             | 101 = Pico       |
+		//	       |        |         |             | 110 = Other      |
+		//	       |        |         |             | 111 = Digipeater |
+		cb := p.data[0] - 33
+		sb := p.data[1] - 33
+		Tb := p.data[2] - 33
+		if p.data[0] != ' ' && ((Tb>>3)&3) == 2 {
+			// CGA sentence, NMEA Source = 0b10
+			d, err := base91Decode(p.data[0:2])
+			if err != nil {
+				return err
+			}
+			p.Altitude = math.Pow(1.002, float64(d))
+			p.Comment = p.data[3:]
+		} else if cb <= 89 { // !..z
+			// Course/Speed
+			p.Velocity.Course = float64(cb) * 4.0
+			p.Velocity.Speed = math.Pow(1.08, float64(sb)) - 1.0
+		} else if cb == 90 { // {
+			// Pre-Calculated Radio Range
+			p.Range = 2 * math.Pow(1.08, float64(sb))
+		}
+	}
+	return nil
+}
+
+func (p *Packet) parseData() error {
+	switch {
+	case len(p.data) >= 1 && p.data[0] == ' ':
+		p.Comment = p.data[1:]
+
+	case len(p.data) >= 7 && strings.HasPrefix(p.data, "PHG"):
+		p.PHG.PowerCode = p.data[3]
+		p.PHG.HeightCode = p.data[4]
+		p.PHG.GainCode = p.data[5]
+		p.PHG.DirectivityCode = p.data[6]
+		p.Range = math.Sqrt(2 * p.PHG.Height() * math.Sqrt((float64(p.PHG.Power())/10)*(float64(p.PHG.Gain())/2)))
+		p.Comment = p.data[7:]
+
+	case len(p.data) >= 7 && strings.HasPrefix(p.data, "RNG"):
+		var err error
+		p.Range, err = strconv.ParseFloat(p.data[3:7], 64)
+		if err != nil {
+			return err
+		}
+		p.Comment = p.data[7:]
+
+	case len(p.data) >= 7 && strings.HasPrefix(p.data, "DFS"):
+		p.DFS.StrengthCode = p.data[3]
+		p.DFS.HeightCode = p.data[4]
+		p.DFS.GainCode = p.data[5]
+		p.DFS.DirectivityCode = p.data[6]
+		p.Comment = p.data[7:]
+	}
+	return nil
+}
+
+func (p Payload) Time() (time.Time, error) {
+	switch p.Type() {
+	case '/', '@':
+		return ParseTime(string(p)[1:])
+	default:
+		return time.Time{}, nil
+	}
+}